Measurement device and method for dynamic stretching crack propagation speed of fragile material

Abstract

The invention discloses a measurement device for the dynamic stretching crack propagation speed of a fragile material. The measurement device comprises an SHPB (split Hopkinson pressure bar) device, a specimen and a high-speed camera, wherein a round through hole is preformed in the center of the specimen, and the specimen is clamped between an incident rod and a transmission rod of the SHPB device; the high-speed camera is installed on an axis of the round through hole of the specimen. The measurement method comprises the following steps: applying impact load to the specimen by utilizing the SHPB device so as to enable a material to be cracked; meanwhile, shooting an image on the surface of the specimen in real time, confirming the crack starting and stopping time according to the record of the image, measuring the length of the crack actually, and calculating the dynamic stretching crack propagation speed. The measurement device and method provided by the invention can control the dynamic stretching crack propagation direction of the fragile material, and also can precisely confirm the crack propagation starting and stopping time, effectively improve the measurement precision of dynamic stretching crack propagation speed of the fragile material, and provide a novel conveniently operated, rapid, convenient, simple and effective method for confirming the dynamic stretching crack propagation speed of the rock-type fragile material under the impact load effect.

Description

technical field [0001] The invention relates to a measuring device and a measuring method for the dynamic tensile crack growth rate of brittle materials, in particular to a measuring device and a measuring method for the dynamic tensile crack growth rate of rock-like brittle materials; belonging to the technical field of brittle material performance measurement. technical background [0002] Crack growth rate is a fundamental parameter in fracture mechanics. Determining the crack growth rate of brittle materials is of great significance for predicting the failure time of brittle materials under the action of accidental loads (such as explosions, earthquakes, etc.) The effect of fracturing also has important engineering practical value. On the other hand, the tensile strength of brittle materials is much lower than its compressive strength and shear strength, and brittle materials usually fail in tension when loaded, so it is more practical to determine the tensile crack gro...

AI Technical Summary

Problems solved by technology

The interpretation of the fracture signal is expressed by the measured voltage difference, and the change of ΔR is a continuous value, so that the change of the pressure difference before the resistance wire is disconnected is a slanted line instead of a ladder, thus giving the interpretation of the fracture time It has brought difficulties; while using pencil leads to monitor crack growth, it is difficult to ensure that the distance between the two pencil leads is small during bonding, so the measured values ​​tend to be more average, which is not ideal in responding to changes in crack speed.

Whether using parallel wire grid strain gauges or sticking pencil leads, the path of crack propagation is blocked, and the whole process of crack propagation cannot be clearly observed, which is not conducive to the analysis of crack propagation characteristics.

This method requires a self-made resistance circuit, pasting a strain gauge with a parallel wire grid and a pencil lead. The operation is complicated and the accuracy of the test result is low.

Images